Microfeed adjusting mechanism



E. F. BRUNS MICROFEED ADJUSTING MECHANISM Dec. l5,v 1970 3 Sheets-Sheet 3 Filed Feb. -1v, 1969 INVENTOR. E/LERT F. BRUNS AT TO PNE YS United States Patent O ware Filed Feb. 17, 1969, Ser. No. 799,8814 Int. Cl. G05g 1/00; F16h 1/38 U.S. Cl. 74-600 9 Claims ABSTRACT OF THE DISCLOSURE A microfeed adjusting apparatus for varying the stroke of a drive arm, wherein a throw block is secured to a main rotary shaft, said throw block being provided with an adjustable T-bolt which is provided with a T-bolt shaft, an eccentric member rotatably mounted on said T-bolt shaft, one end of said drive arm being rotatably mounted on said eccentric member, a iirst gear fixed on said eccentric member, a second gear iqred on said T-bolt shaft, a differential gear means interconnecting said rst and second gear members for rotating the first gear relative to the second gear to move said eccentric member about said T-bolt shaft to change the position of the eccentric member relative to the T-bolt shaft and thus change the length of the stroke of the drive arm, and to maintain the relative adjusted position of the eccentric member, and means for operating said diiferential gear means to change the position of the eccentric member relative to the T-bolt shaft.

BACKGROUND OF THE INVENTION Field of the invention This invention relates generally to metal strip stock feeding apparatuses of the reciprocating rack type, and more particularly, to a microfeed adjusting mechanism for varying the stroke of the drive arm of a strip stock feeding apparatus to adjust the length of the strip stock being fed to a strip stock processing machine.

Description of the prior art Microfeed adjusting mechanisms are well known in the art. One example of the prior art is disclosed in the United States Baringer et al. Pat. No. 3,244,023 in which a metal strip stock feeding apparatus of the reciprocating rack type is controlled by means of a drive arm eccentrically mounted on a T-bolt shaft carried on a trunnion and wherein a gear type means is provided for rotating the eccentric relative to the drive arm to vary the stroke of the drive arm.

A disadvantage of the aforementioned prior art device is that it is large and contains many highly machined parts which are costly to manufacture.

SUMMARY OF THE INVENTION The present invention relates to a metal strip stock feeding apparatus, and more particularly, to a microfeed adjusting mechanism for feeding devices of the reciprocating rack type. The prior art microfeed adjusting mechanisms have certain inherent disadvantages due to their largeness and numerous parts. The prior art devices include many highly machined parts which increase the cost of such devices. Furthermore, many of the prior art devices require auxiliary power equipment, such as air cylinders, hydraulic cylinders, or electric motors, for operating those devices.

In view of the foregoing, it is an important object of the present invention to provide an improved microfeed adjusting mechanism for a strip stock feeding apparatus which overcomes the aforementioned disadvantages of the prior art microfeed adjusting mechanisms.

It is another object of the present invention to provide an impuoved microfeed adjusting mechanism of the class described which includes few parts, is enclosed, selfcontained and lubricated.

It is still another object of the present invention to provide an improved microfeed adjusting mechanism of the class described which is compact in construction, efficient in operation and economical to manufacture.

It is another object of the present invention to provide a microfeed adjusting mechanism for a strip stock feeding apparatus in which the length of the strip stock being fed to a processing machine can be Iquickly and accurately adjusted, either while the feeding apparatus is in operation or while the feeding apparatus is stopped.

It is a further object of the present invention to provide a microfeed adjusting mechanism for varying the stroke of a drive arm, and wherein a throw block is secured to a main rotary shaft, said throw block being provided with a T-bolt adjustably mounted therein and which is provided with a T-bolt shaft, an eccentric member rotatably mounted on said T-bolt shaft, one end of said drive arm being rotatably mounted on said eccentric member, a first gear Xed on said eccentric member, a second gear lixed on said T-bolt shaft, a differential gear means interconnecting said first and second gear members for rotating the first gear relative to the second gear to move said eccentric member about said T-bolt shaft to change the position of the eccentric member relative to the T-bolt shaft and thus change the length of the stroke of the drive arm and for maintaining the relative positions of the throw block and drive arm during rotation of the throw block, and means for operating said differential gear means to change the relative positions of the eccentric and drive arm.

Other objects, features and advantages of this invention will be apparent from the following detailed description, appended claims, and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. l is a side view of a microfeed adjusting mechanism made in accordance with the principles of the present invention.

FIG. 2 is a right end elevational view of the structure illustrated in FIG. l, takenalong the line 2 2 thereof, and looking in the direction of the arrows.

FIG. 3 is a section view of the structure illustrated in FIG. 4, partly in elevational section and partly in horizontal section, taken along the line 3-3 thereof, and looking in the direction of the arrows.

FIG. 4 is a right end elevational view of the structure illustrated in FIG. 3, taken along the line 4-4 thereof, and looking in the direction of the arrows.

FIG. 5 is a fragmentary, horizontal section view of the differential gear structure shown in FIG. 4, with parts shown in phantom, taken along the line 5-5 thereof, and looking in the direction of the arrows.

FIG. 6 is an elevational section view of a handwheel employed in the microfeed adjusting means of the present invention.

FIG. 7 is a fragmentary, top plan view of the structure illustrated in FIG. 6, taken along the line 7-7 thereof, and looking in the direction of the arrows.

3 FIG. 8 is a schematic illustration of a power means for actuating the microfeed adjusting means of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, and in particular to FIG. 1, an illustrative embodiment of the invention 1s shown which is adapted to be used in conjunction with a conventional metal working machine, such as a press t perform punching, cutting or forming of strip stock material being fed thereto. The strip stock material is fed into the punch press, or the like, in an intermittent manner and in timed relation with the reciprocating movements of a metal Working member of the machine, such as a plunger actuated die in a punch press. The strip stock material is fed to the press by feeding rolls on either one or both sides thereof, or on either end or both ends thereof. The feeding rolls may also be self-contained in a separate housing. For the purpose of disclosing the microfeed adjusting mechanism of the present invention, only the crank arm and reciprocating rack have been shown. The function of the rotating crank arm and reciprocating rack, and their relation to a metal working machine, such as a punch press, is well known to those skilled in the strip stock feeding art. However, reference is made to U.S. Pat. No. 3,244,023, dated Apr. 5, 1966, entitled Microfeed Adjusting Mechanism wherein a microfeed adjusting mechanism is illustrated as operatively connected to a punch press, and with a pair of strip stock feeding rolls. The microfeed adjusting mechanism of the present invention would be operatively connected to a metal working machine and a pair of strip stock feeding rolls in the same manner as illustrated in this patent.

As shown in FIG. 3, a conventional throw block 10 of a metal working machine, such as a punch press, is shown in cross section and it is illustrated as being operatively connected to the drive shaft 14 of the press. The throw block 10 has an annular plate 11 releasably secured thereto by a plurality of machine screws 12. The plate 11 is provided with a hub 13 in which is releasably fixed the drive shaft 14 by a key 15.

The throw block 10 is provided with the usual T-slot 16 in which is slidably mounted a conventional T-bolt '17. The T-bolt 17 is adapted to be adjusted to a desired position in the T-slot 16 by the usual adjusting screw 18. The T-bolt 17 is provided with a shaft 19 on which is operatively mounted the reciprocating rack 20.

As shown in FIG. 1, the reciprocating rack 20 is provided on one end with the usual set of linear gear teeth 21 which mesh with and drive a pinion 22 that is operatively mounted on the pinion shaft 23. The pinion shaft 23 is operatively mounted in a rack and pinion housing 24. The pinion shaft 23 is adapted to be operatively connected to a pair of strip stock feeding rolls for operating the rolls in timed relationship to the intermittent operation of the metal working machine in the same manner as illustrated in the aforementioned U.S. Pat. No. 3,244,023. The pinion housing 24 is supported by the pinion shaft 23. As shown in FIG. 3, the reciprocating rack 20 is provided on the other end thereof with a circular opening 27 in which is fixedly mounted by any simple means, as by welding, a bearing housing 28. Operatively mounted within the bearing housing 28 is a pair of roller bearings 29. The inner races of the bearings 29 are seated on a reduced annular surface 32 which is formed on the exterior surface on one end of the hub 33. The surface 32 is formed eccentric to the inner bore through the hub 33 and to the remaining exterior annular surface of the hub. The bearings 29 are retained against axial movement relative to the housing 28 and the hub 33 by a pair of releasable retainer rings and a releasable retainer ring 31.

The hub 33 is supported at its outer end by the internally mounted roller bearing means 34 which is operatively mounted around the outer end of a sleeve shaft 35. The roller bearing means 34 is adjusted to seat at its inner end against the shoulder 36 formed on the internal diameter of the hub 33. A releasable retainer ring 37 maintains the roller bearing means 34 in an axial position against the shoulder 36. The sleeve shaft is provided with a radially extended flange 38 on the outer end thereof which abuts the inner face of the throw block 10. The sleeve shaft 35 is provided with an axial extension or lip 39 on the outer face of the ange 38 which is seated in the outer end of the T-slot 16. A suitable seal 40, as lan O-ring, is mounted around the T-bolt shaft 19, in a suitable slot formed in the bore of the sleeve shaft 35. The inner end of the hub 33 is supported on the T-bolt shaft 19 by a suitable ball bearing means 41 that has its inner race abutting the inner end of the sleeve shaft 35 and its outer race abutting a shoulder on the internal bore of the hub 33. The ball bearing means 41 is retained in axial position by a suitable releasable retainer ring 42.

As shown in FIG. 3, the outer end of the hub 33 extends into the bearing housing 28. The inner end of the hub 33 is enclosed by a suitable housing comprising an annular wall portion 43 which is internally formed with a transverse wall portion 44. The wall portion 44 is formed with a circular flange or hub through which is formed an opening for the reception of the T-bolt shaft 19, the sleeve shaft 35, the hub 33, and the hereinafter described supporting bearing means and gear differential unit.

As shown in FIG. 3, a suitable ball bearing means 46 supports the hub 33 in the housing hub 45. The ball bearing means 46 is retained in axial position by a pair of releasable retainer rings 47 and 48. A suitable seal ringA means 49 is mounted in the hub 45 against the retainer ring 47.

As shown in FIG. 3, the inner end of the hub 33 and the hereinafter described gear dilferential unit is enclosed by a housing extension comprising the annular housing wall 50 which is attached by a plurality of socket head screws 51 to the housing annular wall 43. Integrally formed with the outer end of the housing annular wall 50 is the transverse sloping housing wall 52 which has formed therein an axial circular flange or hub 53 that supports a ball bearing means 54. The outer end of the T-bolt shaft 19 is supported by the ball bearing means 54. A suitable sealing ring means 55 is mounted in the outer end of the opening formed through the hub 53 and it operatively engages the outer annular surface of a presser ring 56. The presser ring 56 is slidably mounted over the reduced and threaded outer end of the T-bolt shaft 19. The reduced end of the shaft 19 terminates at the shaft shoulder 57. The presser ring 56 is adapted to be moved inwardly against the inner race of the ball bearing means 54 by a suitable lock nut 59 for maintaining the bearing means 54 in position.

As shown in FIGS. 3 and 4, a triangularly shaped bracket 60 is integrally attached to the housing annular wall 43 and it extends parallel to the reciprocating rack 20. The bracket `60 carries a hub 61 on the outer end thereof through which is formed a threaded bore 62 for the threaded reception of a shaft v63. The shaft 63 has operatively mounted on one end thereof a cam roller 64 which is rollably mounted in a cam guideway 65 that is formed as a rectangular slot disposed parallel with the longitudinal axis of the reciprocating rack 20. The cam guideway 65 is formed in a cam plate 66 which s fixedly mounted on a mounting plate 67. The mounting plate 67 is xedly mounted by any suitable means, as by welding, on the reciprocating rack 20.

As shown in FIGS. l, 3 and 4, a cylindrical worm gear housing 68 is integrally formed on one side of the housing wall 43 and it encloses a worm gear 69 which is mounted on a shaft 70. As shown in FIG. 4, the shaft 70 has the reduced outer ends 71 and 76 which are rotatably mounted in a pair of suitable bearings 72 and 75, respectively. The ends of the housing 68 are enclosed by a pair of suitable end `plates 73 which are secured in place by a plurality of socket head screws 74.

As shown in FIG. 3, the worm gear 69 is adapted to mesh with and drive a worm wheel 77 which is mounted for rotation about the hub 33. The worm wheel 77 is formed on a plate which has an axial bore 78 formed therethrough in which is mounted a suitable ball bearing means 79 for rotatably mounting the worm wheel 77 on the outer surface of the hub 33. The outer race of the bearing 79 is releasably secured against axial movement in the bore 78 by a pair of releasable retainer rings 80. A spacer 81 is mounted between the bearing 79 and the bearing 46 for retaining the inner race of the bearing 79 against a shoulder 82 formed on the exterior surface of the hub 33.

As shown in FIGS. 3 and 5, a differential gear carrier is carried by the worm wheel 77. The last mentioned `carrier includes the integral annular wall 83 which extends axially over the hub 33 and the T-bolt shaft 19. Releasably secured to the outer end of the carrier wall 83 is a transverse carrier wall portion 84 which is secured to the carrier wall portion 83 by any suitable means, as by a plurality of socket head machine screws 85. The outer end of the T-bolt shaft 19 extends through a bore formed through the carrier Wall 84 and supports the carrier wall 84 by means of a suitable ball bearing means 86. The ball bearing means 86 is releasably secured in an axial position on the T-bolt shaft 19, and in the bore formed through the carrier wall 84, by a pair of spacer The aforementioned worm wheel carrier carries a differential gear unit or mechanism which is illustrated in FIGS. 3 and 5. As best seen in FIG. 5, the differential gear unit includes a pair of gear sleeve shafts 88 and 88a which are each rotatably mounted by a pair of roller bearing means as 489 and 90, and 89a and 90a, respectively, on a pair of laterally spaced apart shafts 91 and 91a, respectively. The inner ends of the shafts 91 and 91a are slidably mounted in suitable bores formed in the body of the worm wheel 77. The outer ends of the shafts 91 and 91a are extended through suitable bores in the carrier transverse plate 84. The outer ends of the shafts 91 and 91a are provided with mounting heads which carry suitable machine screws 92 and 92a for securing the shafts 9'1 and 91a, respectively, in place. The roller bearing means 89 and 90 are axially spaced apart by the spacer member 93 and they are retained in axial position relative to the gear shaft 88 by a pair of suitable releasable retainer rings 94. The bearing members 89a and 90a are also spaced apart by a spacer 93a and retained in axial position in the gear shaft 88a by a pair of releasable retainer rings 94a.

As illustrated in FIGS. 3 and 5, an elongated gear 100a is formed on the gear shaft 88a, and it is meshed with a gear 95 that is fixed on the T-bolt shaft 19. The gear 95 is fixed on the T-bolt shaft 19 by a suitable key 99 and it is spaced between the hub bearing means 41 and the carrier spacer 87 by a spacer ring 98. As shown in FIG. 5, the teeth of the gear 100a are axially longer than the gear teeth on the gear 496 and they extend laterally toward the worm wheel 77 and mesh with a similar gear 100 which is formed on the other gear shaft 88. As illustrated in FIGS. 3 and 5, the elongated gear 100 meshes with and drives a narrower gear 96 which is integrally formed on the exterior of the hub 33, at the inner end thereof. It will be seen that when the worm gear 69 turns the worm wheel 77 the carrier will be rotated, and by means of the differential gear unit acting upon the gears 95 and 96 the hub 33 is rotated so as to rotate the eccentric portion 32 of the hub 33, and adjust the position of the rack relative to the throw block 10. The means for rotating the worm gear 69 to provide the aforementioned adjustment of the rack 20 relative to the throw block 10 is carried out by the following described structure.

As shown in FIG. l, the reduced end shaft 76 on the gear 69 (FIG. 4) extends outwardly of the gear housing 68, and it is operatively connected to one end of a suitable universal joint means 101. The other end of the universal joint means 101 is operatively connected to one end of an elongated control shaft 102, which has its other end slidably connected to one end 103a of a second universal joint means generally indicated by the numeral 103. Said other end of the shaft 102 is slidably mounted in a bore in the universal joint means end member 10'3a, and it carries a cross pin 103b which has the extended ends thereof slidably mounted in a pair of longitudinal slots, as 103e, to permit relative axial movement between the joint means 103 and the shaft 102. The other end of the universal joint means 103 is operatively connected to the reduced front round end of a square shaft 104. The square shaft 104 has` a reduced rear round end. As shown in FIG. l, the round ends of the square shaft 104 are rotatably mounted in the bearings 105 and 106 which are carried in a pair of longitudinally spaced apart front and rear support brackets 107 which are fixed on the reciprocating rack 20. The reduced round rear end of the square shaft 104 is threaded, and it is secured in place relative to the rear support bracket 107 by a suitable lock nut 108.

As shown in FIG. 1, the square shaft 104 is slidably mounted through an axial square hole 109a in the gear 109 which is rotatably mounted by any suitable means in a support bracket 110. As shown in FIGS. 1 and 2, the support bracket 110 is mounted on a plate 113 which in turn is fixed by any suitable means to the bracket and pinion housing 24. As shown in FIG. l, the gear 109 is meshed with and driven by a second gear 111 which is also rotatably journalled in the support bracket 110. The gear 111 is fixed to a drive shaft 112 which is operatively connected by a suitable coupling 114a to a suitable flexible shaft 114.

As shown in FIG. 6, the flexible shaft 114 is connected by any suitable means, as by the coupling 114b and two pins 114e to the one end of a handwheel control shaft generally indicated by the numeral 115. Fixedly mounted on the other end of the shaft 115 by a pin 117 is a control handwheel 116. The shaft 115 is rotatably mounted by a suitable pair of sleeve bearing members 118 and 122 in a pair of spaced apart, Vertical support walls 119 and 121, respectively. The shaft 115 is held against axial movement by a retainer ring 123 that is slidably mounted over the shaft 115 and secured in place by a suitable pin 124.

The shaft 115 is provided with a suitable indicator means which is calibrated to show the amount of adjustment of the reciprocating rack 2.0` relative to the throw block 10, and to show the direction of adjustment of the length of the strip stock. As shown in FIG. 6, the control shaft 115 is provided with a centrally disposed threaded portion 125 which is threadably mounted through the threaded bore 131 formed in a carrier nut member 126. The carrier nut member 126 has the lower end in sliding engagement With the upper surface of the plate 120, whereby when the threaded shaft portion 125 is turned, the carrier nut 126 will be moved axially relative to the shaft 115 but will be restricted from rotating. The carrier nut 126 carries an indicator .finger which has a horizontal portion 127 that extends through a slot 128 formed in a plate 129 that is xedly mounted, by any suitable means, on the upper ends of the walls 119 and 121. The indicator finger portion 1217 coacts with the calibrated indicia on the outer face of the plate 129, which is calibrated in fractions of an inch, to show a change in the length of the strip stock being fed to a machine. The plate 129 is also calibrated to indicate in which direction the handwheel 116 is to be turned when the length of strip stock is to be shortened or lengthened, by means of the capital letters S and L which are `disposed in spaced apart positions with arrows pointing toward these letters. The indicator mounting plate 120 may be secured in any suitable mounting position, as for example, on a portion of a press or the like, by any suitable means, as by the socket head screws 130 shown in FIG. 7.

In operation, the length of the stroke of the rack 20 may be quickly and easily changed by rotating the handwheel 116 in either direction to either lengthen the stroke, or shorten the stroke, as desired. It will be seen that when the handwheel 116 is turned, the shafts 112 and 114 will be turned. The shaft 112 rotates the gears 111 and 109. The gear 109 turns the square shaft 104 which rotates the shaft 102' and the worm gear 69. The worm gear 69 rotates the worm wheel 77 and the carrier member carrying the differential gears 100 and 100a. The rotation of the carrier member and the differential gears 100 and 100:1 will rotate the worm gear 96 and the hub 33 relative to the gear 95 which is fixed on the T-bolt shaft 19` so as to rotate the eccentric 32 relative to the T-bolt 19 and thus change the length of stroke of the rack 20. It will be understood that the adjusting of the length of stroke of the rack 20 may be carried out while the machine is in operation or while it is stopped. It will be understood that the adjusting means of the present invention provides for a ne adjustment of the length of stroke of the rack 20, and that the adjusting screw 18 provides for a coarse adjustment of the rack '20 in a conventional manner.

It will be understood that while the press is in operation, the gears 95, 96, 100 and 100a are continuously rotating to drive the eccentric 32, to maintain it in the proper adjusted position relative to the T-bolt shaft 19. The worm gear 69 and the worn wheel 77 are rotated only when an adjustment is to be made to adjust the eccentric 32 relative to the T-bolt shaft 19, either while the press is running or while it is stopped.

FIG. 8 is a schematic illustration of a power means for actuating the microfeed adjusting means of the present invention. The numeral 134 generally designates a suitable hydraulic or electric power motor having a suitable gear reduction means and an output shaft 135 which is shown as being connected to the flexible shaft 114 by a suitable coupling 114d. The power motor 134 may be controlled by any suitable means, and it would provide a power substitute means for the manually operated handwheel 116, if desired.

It will be seen that the housing which encloses the microfeed adjusting gear means of the present invention comprises an enclosed housing which provides a self-contained and lubricated device. As shown in FIG. 3, lubricating fluid may be added to the bearings 29 through the port 132 and to the interior of the housing by means of the inlet port 133.

While it will be apparent that the preferred embodiments of the invention herein disclosed are well calculated to fulfill the objects above stated, it will be appreciated that the invention is susceptible to modification, variation and change.

I claim:

1. In a drive stroke adjusting appartus for varying the stroke of a drive arm, wherein a throw block is secured to a main rotary shaft, said throw block is provided with a T-bolt adjustably mounted therein and which is provided with a T-bolt shaft, the combination comprislng:

(a) an eccentric member rotatably mounted on said T-bolt shaft;

(b) one end of said drive arm being rotatably mounted on said eccentric member;

(c) a first gear fixed on said eccentric member;

(d) a second gear fixed on said T-bolt shaft;

(e) a differential gear means interconnecting said first and second gear members for rotating the first gear relative to the second gear to move said eccentric member about said T-bolt shaft to change the position of the eccentric member relative to the T-bolt shaft and thus change the length of the stroke of the drive arm;

(f) a carrier member operatively supporting said differential gear means and being rotatably mounted about said T-bolt shaft; and,

(g) means for operating said differential gear means.

2. The drive stroke adjusting apparatus as defined in claim 1, wherein said means for rotating said carrier member includes:

(a) a housing enclosing said T-bolt shaft, said first gear, said second gear, said differential gear means and said carrier member;

(b) means rotatably mounting said T-bolt shaft, said first gear, and said carrier member within said housmg;

(c) means connecting said housing to said drive arm to restrict movement of said housing relative to said drive arm except along the longitudinal axis of said drive arm; and

(d) means carried by said housing for operative engagement with said carrier member for rotating said carrier member about said T-bolt shaft for operating said differential gear means to rotate said first gear relative to said T-bolt shaft.

3. The drive stroke adjusting apparatus as defined in claim 2, wherein:

(a) said carrier member is provided with a worm wheel; and

(b) said means carried by said housing for operative engagement with said carrier member includes a worm gear rotatably mounted in said housing and being in driving engagement with said worm wheel for rotating said carrier member.

4. The drive stroke adjusting apparatus as defined in claim 3, wherein:

(a) said means for operating said differential gear means further includes a manually operable means connected to said worm gear for rotating the worm gear.

5. The drive stroke adjusting apparatus as defined in claim 4, wherein said manually operable means includes:

(a) an elongated shaft means; and

(b) a handwheel operatively connected to said elongated shaft means.

6. The drive stroke adjusting apparatus as defined in claim 5, wherein said manually operable means further includes:

(a) an indicator means operated by said handwheel to indicate the amount of adjustment of said drive arm.

7. The drive stroke adjusting apparatus as defined in claim 5, wherein:

(a) said drive arm comprises an elongated rack operatively connected to a member to be driven by the drive arm;

(b) said handwheel is mounted on a drive mechanism operated by said rack; and

(c) said elongated shaft means includes a shaft means mounted on said rack and having a square shaft portion thereof slidably connected to a gear means operatively connected to said handwheel.

8. The drive stroke adjusting apparatus as defined in claim 1, wherein said differential gear means includes:

(a) a first differential gear meshed with said second gear and rotatably mounted on said carrier member;

(b) a second differential gear meshed with said first gear and rotatably mounted 0n said carrier member; and,

(c) said first and second differential gear members being elongated and meshed with each other.

9. The drive stroke adjusting apparatus as defined in claim 3, wherein:

(a) said means for operating said differential gear means further includes a power operated means connected to said Worm gear for rotating the worm gear.

References Cited UNITED STATES PATENTS 1,723,231 8/ 1929 Ellsworth 74--675 2,266,237 12/ 1941 Newell 74-675 3,216,277 11/1965 Groll 74-600 10 3,244,023 4/ 1966 Baringer et al. 74*600 2,856,793 10/ 1958 Budlong. 3,076,368 2/1963 Groll.

5 WESLEY S. RATLIFF, I R., Primary Examiner U.S. Cl. X.R. 74-675 

